Foil, as defined in A Concise Encyclopedia of Metallurgy, by A. D. Merriman, MacDonald and Evans LTD. 1965, is a very thin sheet metal with no standard thickness, but it is generally regarded as being intermediate in thickness between "leaf" and sheet. A Glossary of Metallurgical Terms and Engineering Tables, published by The American Society for Metals, in 1983, lists a definition for foil as "a metal in sheet form less than 0.15 mm (0.006 inches) in thickness." As used herein, the term "foil" designates a thin layer of metal having a thickness range of about 0.005-0.017 inches.
A process for making foils is disclosed in U.S. Pat. No. 4,917,858. U.S. Pat. No. 4,917,858 teaches blending a powder of titanium with a powder of aluminum in preselected proportions and rolling the mixed powders to a predetermined thickness to form a foil of a titanium-aluminum alloy and then sintering the rolled foil followed by hot pressing the foil to densify the foil to near theoretical density. U.S. Pat. No. 4,917,858 also discloses the incorporation of a third metal powder as an alloying element. Niobium, molybdenum, vanadium, chromium, manganese, erbium, and yttrium are listed as candidate third powder additives. The drawback of this method is that several intermediate steps, such as rolling, vacuum sintering, and pressing, must be carried out in order to obtain thin foils. Further, U.S. Pat. No. 4,917,858 is limited to utilizing powders of single elements and their alloys to form a foil.
Therefore, it is desirable to provide a method for making foils compatible with a variety of prealloyed compositions, preferably in powder form, and particularly with admixtures of prealloyed powders having different physical properties (e.g. different melting points and softening points), which provides greater improvement of alloy composition, thereby allowing low ductility alloy foils to be manufactured.
Additionally, it is desirable to provide alloy foils that can be utilized in repair and joining operations.